The investigation of cell lines derived from human teratocarcinoma can provide information pertinent to human embyonic cells, and to the clinical management of these tumors. We shall relate such cell lines to the various cell types found in human teratocarcinoma, and characterize the cell surface antigens and secreted proteins (HCG and AFP) that they express. Our preliminary data indicate that these human tumors differ significantly from murine teratocarcinoma. New monoclonal antibodies recognizing differentiation antigens of human teratocarcinoma cells will be produced. We shall use these as probes for tumor location by external scintigraphy in the athymic (nu/nu) xenograft model. Heterogeneous cell lines that appear to contain pluripotent stem cells capable of differentiating in culture will be recloned to prove that differentiation does (e.g. cell density, chemical induction by retinoic acid, etc.) will be determined. Using specific markers, especially cell surface differentiation antigens that characterize different cell types, we shall document the cell types produced, and use immunoselection techniques (fluorescence-activated cell sorting, complement-mediated cytotoxicity, etc.) to isolate them. We shall investigate the stability of each cell type and potential for further differentiation, and thus identify the stem celland the pathways by which it differentiates. Pluripotent human teratocarcinoma stem cells provide a unique opportunity to study the expression of genes that are regulated in early human development. We shall use existing cDNA probes to investigate how transcription, RNA processing and translation mediate the control of HCG production during the differentiation of human EC cells into trophoblast.